<style>
	.parent{
		position:relative;
		width:300px;
		height:300px;
		background:#009933;
	}
	
	.children{
		width:100px;
		height:100px;
		background:#31B0D5;
		position:absolute;
		top:40px;
		left:40px;
	}
</style>

<div class="parent">
	<div class="children"></div>
</div>

<script type="text/javascript" src="lib/jquery-2.1.0.min.js" ></script>
<script type="text/javascript" src="js/tool.js" ></script>
<script>
	$(".children").click(function(e){
		console.log(JSON.stringify($(this).offset()));
		console.log(JSON.stringify(commonTool.domPosition(this)));
	});
</script>